Ground Battle Formula

Here is the math to Ground Battle. It is not exact, but it gives you a rough estimate to get a good battle odds (65-85%):
Input needed:
-Assume DEFCON levels of both nations are the same
-Your Nation NS
-Enemy Nation NS
-Your soldier efficiency percentage (see above to count it)
-Enemy's soldier efficiency

NS formula% = Your NS / (Your NS + Enemy NS)
Number of soldiers to deploy = ((Enemy soldier efficiency * NS formula) + Enemy soldier efficiency) / Your soldier efficiency percentage.

Example:
My NS: 13,299
Enemy NS: 13,287
My efficiency (Aluminum, Pigs, Coal, Democracy): 61%
Enemy soldier efficiency: 8,564

NS formula = 13,299 / (13,299 + 13,287) = 50.02%
Number of soldiers to deploy = ((8,564 * 50.02%) + 8,564) / 61% = 21,075

Based on the calculation above, I should deploy 21,075 to get a good winning odds.